Spine Stereotactic Body Radiotherapy Research Articles

Mature Outcomes of Stereotactic Body Radiotherapy for Spinal Metastases with 30 Gy in 4 Fractions

<h3>Purpose/Objective(s)</h3> At our institution, 30 Gy in 4 spine stereotactic body radiotherapy (SBRT) fractions is typically delivered for larger volume when multiple segments are included in the treatment volume and/or for the retreatment of spinal metastases. We report MRI-based local failure (LF) and vertebral compression fracture (VCF) rates for patients (pts) treated with 30 Gy/4Fx of spine SBRT. <h3>Materials/Methods</h3> A retrospective analysis of all pts with spine metastases treated with 30 Gy/4Fx from 2010 to 2021 from an institutional registry was performed. Demographic, clinical, dosimetric, and radiological data were summarized, and the primary endpoint was the MRI-based LF rate. Secondary endpoints included the incidence of VCF and overall survival (OS). Kaplan Meier was used to calculate LF and VCF per segment and OS per patient. <h3>Results</h3> Were included 116 pts with 245 treated segments in this analysis. The median number of consecutive segments in the treatment volume was 3 (1-7), and the median clinical target volume (CTV) was 126 cc (range, 10-863). Kidney (25%), lung (20%), breast (19%), prostate (19%), and colon (10%) cancer were the most common primary histologic types. 38% of pts had oligometastatic disease and 24% spine metastases only. 15% (17/116) of the patients were treated with postoperative SBRT. 31% of segments were re-irradiated for conventional palliative radiation, and 26% prior SBRT, failures. 25% of segments had a baseline VCF, 46% epidural disease, and 53% paraspinal tumor extension. The median follow-up per patient was 18.5 (range, 0.1-61) and per segment 10.7 mos (range, 0.1-59). The LF rates at 12 and 24 mos were 10.7% (95% CI 7.1-15.2) and 16% (95% CI 11.5-21.2), and for VCF were 7.3% (95% CI 4.4-11.2) and 11.2% (95% CI 7.5-15.8), respectively. 60% of failures had an epidural, and 23% a paraspinal, component. Age <68y (HR=0.43, 95% CI 0.19-0.95, p=0.038), volume of CTV <72cc (HR=0.09, 95% CI 0.01-0.70, p=0.021), and prior surgical stabilization (HR=0.25, 95% CI 0.07-0.81, p=0.021) were protective predictors for VCF on multivariable analyses (MVA). In particular, the VCF rate at 24 mos was 1.8% for pts with CTV volume <72 vs 14.6% for ≥72cc. Median OS was 20.3 mos (95% CI 14.8-27.1). Low grade or no epidural disease (HR=0.42, 95% CI 0.21-0.84, p=0.014), paraspinal disease (HR=3.07, 95% CI 1.68-5.62, p<0.001) and kidney primary cancer (HR=2.43, 95% CI 1.08-5.44, p=0.031) were predictors for OS on MVA, with a trend for oligometastatic disease (HR=0.56, 95% CI 0.31-1.02, p=0.059). No radiation-induced myelopathy was observed. <h3>Conclusion</h3> This first report for 30 Gy/4Fx as a novel fractionation for spine SBRT suggests high rates of local control and a low rate of VCF, particularly for those target volumes with a CTV<72 cc. However, our rate of VCF in very large treatment volumes (≥72cc) is comparable to the SBRT-induced VCF literature, where optimal management remains an active area of investigation.

An Externally Validated RPA-Based Pre-Treatment Decision-Making Tool Identifying Ideal Candidates for Spine SBRT

<h3>Purpose/Objective(s)</h3> We sought to develop and validate a novel decision-making tool predictive of overall survival (OS) for patients receiving stereotactic body radiation therapy (SBRT) for spinal metastases. <h3>Materials/Methods</h3> Treatments were performed at two institutions and most commonly involved one or three fractions of spine SBRT. Recursive partitioning analysis (RPA) was conducted using decision-tree analysis. Potential correlations between variables were assessed with a correlation heatmap. OS was analyzed using the Kaplan-Meier method. Exclusion criteria included: treatments with proton therapy, benign primary histologies, missing variables of interest, and patients with the first course of spine SBRT outside of the participating institutions. <h3>Results</h3> The initial dataset consisted of 424 patients with 522 treated lesions. Of these, 361 patients were used for the RPA and initial model development because not all components of the SINS score were available for 63 patients. After consideration of 9 candidate variables, the final model consisted of the following variables and corresponding scores: SINS ≥ 6 (1); time from primary diagnosis < 21 months (1); ECOG performance status = 1 and ECOG > 1 (1 and 2, respectively); and > 1 organ systems involved (1). Each variable was an independent predictor of OS (p<0.001), and each 1-point increase in score was associated with a hazard ratio of 2.01 (95% confidence interval (CI): 1.79-2.25, p<0.0001) (Table). The concordance value was 0.75 (95% CI: 0.71-0.78). The scores were then discretized into 3 groups: favorable (score: 0-1), intermediate (score: 2), and poor (score: 3-5) survival, with 2-year OS of 84% (95% CI: 79-90%), 46% (95% CI: 36-59%), and 21% (95% CI: 14-32%), respectively (p<0.0001 for each). In the external validation set (182 patients), the score was predictive of OS (p<0.0001). The favorable, intermediate, and poor survival groups each demonstrated statistical significance (p<0.002), with 2-year OS of 77%, 50%, and 36%. Increasing SINS score was predictive of decreased OS as a continuous variable, with a hazard ratio of 1.17 (95% CI: 1.12-1.23, p<0.0001). Of the 6 components of the SINS score, 4 demonstrated associations with OS: pain, type of bone lesion, vertebral body collapse, and posterior spinal element involvement. <h3>Conclusion</h3> We propose this novel score as a decision-making tool to help optimize patient selection for spine SBRT. The SINS score may be an independent predictor of OS.

Planning for the Impact of SC.24 on Spine Stereotactic Body Radiotherapy (SBRT) Utilization at a Tertiary Cancer Center

<h3>Purpose/Objective(s)</h3> CCTG SC.24 was a recently reported randomized phase 2/3 trial that demonstrated superior complete response rates for pain following spine stereotactic body radiotherapy (SBRT; 24 Gy in 2 daily fractions) compared to conventional radiotherapy (CRT; 20 Gy in 5 fractions). These findings support a practice-changing paradigm shift whereby a subset of eligible patients with painful spine metastases may be offered upfront spine SBRT over CRT. At many institutions, this would mark an increase in spine SBRT cases. Therefore, we sought to assess the potential real-world impact of this study on spine SBRT utilization by estimating the proportion of patients treated with CRT who would have been eligible for spine SBRT per SC.24 inclusion criteria. <h3>Materials/Methods</h3> All patients who received palliative spine radiation at our institution between August to October 2020 were reviewed retrospectively. Data extracted included eligibility criteria of the SC.24 study, provider-reported pain response, and overall survival. Descriptive statistics and survival analyses were performed. <h3>Results</h3> Of the 73 patients reviewed, 24 (33%) patients met eligibility criteria for SC.24. The most common exclusion factors included irradiation of more than 3 consecutive spinal segments (n=32, 44%), ECOG greater than 2 (n=17, 23%), symptomatic spinal cord compression (n=13, 18%), and frank mechanical instability (n=12, 16%) as measured using the Spinal Instability in Neoplasia Score (SINS). SINS was indeterminable in 7 cases (10%) of epidural-only disease, which also renders a patient ineligible; otherwise, the median SINS was 9 (IQR: 7–10). Four (5%) patients had prior surgery and 8 (11%) patients had prior overlapping radiation to the area, also rendering them ineligible. Of eligible patients, the mean age was 68.92 years (SD 13.84), median SINS was 8 (IQR: 7–9) and median ECOG was 2 (IQR: 1–2). The most common primary cancer types among eligible patients were lung (n=10) and breast (n=4). The median dose delivered to eligible patients was 20 Gy in 5 fractions (IQR: 8–20 Gy). Fifteen (63%) eligible patients had additional radiation to a site other than the spine at the same time. The median survival of eligible patients was 10 months (95% CI: 4 months–not reached) with 58% surviving longer than 3 months. 75% of patients had pain response documented and of these, 54% had at least some response after CRT. <h3>Conclusion</h3> Around 1/3 of patients who received palliative CRT to the spine met eligibility criteria for SC.24. This possible expanded indication for spine SBRT can have a substantial impact on resource utilization. In addition to increased MR simulation utilization, there can also be higher demand on contouring, planning and quality assurance resources. These data may be useful in guiding resource and workforce planning at institutions looking to commence or expand a spine SBRT program.

Dose-Escalated Two-Fraction Spine Stereotactic Body Radiotherapy: 28 Gy vs. 24 Gy in 2 Daily Fractions

<h3>Purpose/Objective(s)</h3> Stereotactic body radiotherapy (SBRT) for spine metastases improves pain response rates and local control compared to conventional external beam radiotherapy, however, the optimal fractionation schedule is unclear. We report local control and toxicity outcomes after dose-escalated two-fraction spine SBRT. <h3>Materials/Methods</h3> A prospectively maintained institutional database of over 600 patients and 1400 vertebral segments treated with spine SBRT, using an established treatment technique, was reviewed to identify those treated with 28 Gy or 24 Gy in two daily fractions. The primary endpoint was MRI-based local failure (LF), and secondary endpoints included overall survival (OS) and vertebral compression fracture (VCF). <h3>Results</h3> A total of 947 treated vertebral segments in 482 patients were identified, of which 159 patients (301 segments, 31.8%) received 28 Gy and 323 patients (646 segments, 68.2%) received 24 Gy in 2 fractions. Median follow-up was 23.5 months and median OS was 49.1 months. In the 28 Gy cohort, the 6-, 12-, and 24-month cumulative incidences of local failure were 3.5%, 5.4% and 11.1%, respectively, vs. 6.0%, 12.5% and 17.6% in the 24 Gy cohort, respectively (p=0.0075). On multivariable analysis, 24 Gy (HR: 1.572, 95%CI: 1.08-2.30, p=0.0196), epidural disease (HR: 1.522, 95%CI: 1.10-2.10, p=0.0108), and paraspinal extension (HR: 1.517, 95%CI: 1.08-2.12, p=0.0151) predicted for greater rates of local failure. Risk of VCF was 5.5%, 7.6% and 10.7% at 6-, 12- and 24-months, respectively, and similar between the two cohorts (p=0.573). Spinal malalignment (p<0.001), baseline vertebral body collapse (p=0.0027), junctional spine location (p=0.0296), and a greater PTVD90 predicted for greater rates of VCF. <h3>Conclusion</h3> 28 Gy in 2 daily fractions was associated with improved local control without increasing the risk of VCF, and the 2-year local control rates fit the HYTEC spine tumor control probability model.

Mature Local Control and Reirradiation Rates Comparing Spine Stereotactic Body Radiotherapy to Conventional Palliative External Beam Radiotherapy

<h3>Purpose/Objective(s)</h3> Stereotactic body radiotherapy (SBRT) improves complete pain response for painful spinal metastases compared to conventional external beam radiotherapy (cEBRT). We report mature local control and reirradiation rates in a large cohort of patients treated with SBRT vs. cEBRT enrolled previously in the Canadian Clinical Trials Group Symptom Control (SC).24 phase II/III trial. <h3>Materials/Methods</h3> 137/229 (60%) patients randomized to 24 Gy in 2 SBRT fractions or 20 Gy in 5 cEBRT fractions were retrospectively reviewed. By including all treated spinal segments, we report on 66 patients (119 spine segments) treated with SBRT, and 71 patients (169 segments) treated with cEBRT. The primary outcomes were MR-based local control and reirradiation rates for each treated spine segment. <h3>Results</h3> The median follow-up was 11.3 months (IQR:5.3-27.7 months), and median OS in the SBRT and cEBRT cohorts were 21.6 and 18.9 months (p=0.428), respectively. The cohorts were balanced with respect to radioresistant histology and presence of "Mass" (paraspinal and/or epidural disease extension). Risk of local failure after SBRT vs. cEBRT at 6, 12 and 24 months were 2.8% vs. 11.2%, 6.1% vs. 28.4% and 14.8% vs. 35.6%, respectively (p<0.001). cEBRT (HR:3.48, 95%CI:1.94-6.25, p<0.001) and presence of "Mass" (HR:2.07, 95%CI:1.29-3.31, p=0.002) independently predicted local failure on multivariable analysis. The 1-year reirradiation rates and median times to reirradiation after SBRT vs. cEBRT, were 2.2% vs 15.8% (p=0.002) and 22.9 months vs. 9.5 months respectively. Radioresistant histology (HR:2.66, 95%CI:1.43-4.94, p=0.002) and cEBRT (HR:2.34, 95%CI:1.14-4.78, p=0.002) independently predicted for reirradiation. 8/12 iatrogenic vertebral compression fractures (VCFs) were after SBRT and 4/12 after cEBRT; Grade 3 toxicities were isolated to the SBRT cohort (5/12). <h3>Conclusion</h3> Risk of local failure and reirradiation is lower with SBRT compared to cEBRT for spinal metastases. Although the iatrogenic VCF rates were within expectations, Grade 3 VCF were isolated to the SBRT cohort.

Optimized workflow to minimise intra-fractional motion during stereotactic body radiotherapy of spinal metastases.

This study evaluated translational and rotational intra-fractional patient movement during spinal stereotactic body radiotherapy (SBRT) using 6D positioning based on 3D cone beam computerized tomography (CBCT) and stereoscopic kilovoltage imaging (ExacTrac). The aim was to determine whether additional intra-fractional image verification reduced intra-fractional motion without significantly prolonging treatment time, whilst maintaining acceptable imaging related dose. A retrospective analysis of 38 patients with 41 primary tumour volumes treated with SBRT between September 2018 and May 2021 was performed. Three different image-guided radiotherapy (IGRT) workflows were assessed. The translational and rotational positioning errors for the different imaging workflows, 3D translational vectors and estimates of imaging dose delivered for the different imaging workflows were evaluated. As the frequency of intra-fractional imaging increased from workflow 1 to 3, the mean intra-fraction 3D translational vector improved from 0.91mm (±0.52mm), to 0.64 (±0.34mm). 85%, 83% and 97% of images were within a tolerance of 1mm/1° for workflows 1, 2 and 3 respectively, based on post treatment CBCT images. The average treatment time for workflow 3 was 13min, as compared to 12min for workflows 1 and 2. The effective dose per treatment for IGRT workflows 1, 2 and 3 measured 0.6mSv, 0.95mSv and 1.8mSv respectively. The study demonstrated that the use of additional intra-fractional stereoscopic kilovoltage image-guidance during spinal SBRT, reduced the number of measurements deemed "out of tolerance" and treatment delivery could be optimized within a standard treatment timeslot without applying substantial additional radiation dose.

Practice Patterns and Perspectives on Stereotactic Body Radiation Therapy for the Metastatic Spine From Lower- and Middle-Income Countries.

We wanted to understand the current practice patterns and stereotactic body radiation therapy (SBRT) utilization for spine metastases in lower- and middle-income countries (LMICs). A questionnaire was designed to identify the current practice patterns of treating spine metastases, uptake of spine SBRT in routine care, dose fractionations commonly used, and the perceived benefits and toxicities of using ablative doses. Individuals registering for a spine SBRT workshop were requested to answer the questionnaire. We received 395 responses from radiation oncologists (ROs) working in 12 different LMICs. The majority of respondents were from an academic institute (57.5%). Two hundred seventy-four respondents further identified themselves from the government/public sector (44.89%), corporate/private sector (47.89%), not-for-profit organization (5.4%), or public-private partnership (5.4%). The respondents indicated that 8.43%, 27.46%, 41.73%, and 10.04% of the spine metastases patients are treated using clinical marking, X-ray-based, 3D conformal radiation therapy, and SBRT, respectively. A third of the respondents did not have any experience of spine SBRT; those with high-volume practice were predominantly from an academic institute. The majority of respondents would use spine SBRT to reduce pain severity (71.9%) and achieve durable pain control (61.01%) in the setting of oligometastases (92.73%) and reirradiation (56.69%). Respondents preferred 3- to 5-fraction regimens (64.9%) over 1-2 fractions (33.68%). The top three reasons for not using spine SBRT were resource constraints (50%), lack of machine (37.11%), and lack of training (27.34%). There is heterogeneity in spine SBRT practice and utilization between academic and nonacademic institutes. Resource and infrastructure constraints along with lack of training are limiting the use of SBRT among ROs from LMICs. Collaborative studies from LMICs will help in resolving unique challenges posed by resource constraints.

79: Planning for the Impact of SC.24 on Spine Stereotactic Body Radiotherapy (SBRT) Utilization at a Tertiary Cancer Centre

79: Planning for the Impact of SC.24 on Spine Stereotactic Body Radiotherapy (SBRT) Utilization at a Tertiary Cancer Centre

83: Dose-Escalated Two-Fraction Spine Stereotactic Body Radiotherapy: 28 GY Versus 24 GY in 2 Daily Fractions

83: Dose-Escalated Two-Fraction Spine Stereotactic Body Radiotherapy: 28 GY Versus 24 GY in 2 Daily Fractions

77: Outcomes of 30GY in 4 Fractions for Spine Stereotactic Body Radiotherapy

77: Outcomes of 30GY in 4 Fractions for Spine Stereotactic Body Radiotherapy

47: Mature Local Control and Reirradiation Rates Comparing Spine Stereotactic Body Radiotherapy to Conventional Palliative External Beam Radiotherapy

47: Mature Local Control and Reirradiation Rates Comparing Spine Stereotactic Body Radiotherapy to Conventional Palliative External Beam Radiotherapy

On-line adaptive and real-time intrafraction motion management of spine-SBRT on an MR-linac

Purpose: The superior soft-tissue contrast of MRI-guided radiotherapy offers enhanced localization accuracy of the spinal cord in spine Stereotactic Body Radiotherapy (SBRT). This work includes a planning study for spine-SBRT on an MR-Linac. Additionally, a patient with spine metastasis was treated using an adaptive radiation therapy workflow. We report our initial experience of targeting accuracy, image-guided localization, on-line adaptive planning, and treatment with real-time intrafraction imaging with automatic beam gating.Methods: Six spine-SBRT patients were retrospectively re-planned to 18 Gy in 1-fraction on a commercial, Monte Carlo-based MR-Linac treatment planning system. Plans were generated using 9–13 step-and-shoot intensity-modulated radiation therapy 6 MV-flattening filter free beams and optimized to achieve plan quality criteria recommended by RTOG-0631. One thoracic vertebral body clinical case was treated to 27 Gy in 3-fractions utilizing ART, where daily anatomical changes were accounted for via re-planning and treatment in an on-line manner to account for limited ability to correct rotational setup uncertainties.Results: Plans met all critical-tissue constraints outlined in RTOG-0631 and AAPM Task Group-101, while covering 90% of the target with the prescription dose. Clinically, visibility of the spinal cord allowed for patient setup focusing on spinal cord-alignment. Utilization of the online ART workflow, while re-contouring the target and spinal cord, enabled an increase in prescription dose coverage from 89 to 95% in two of three fractions while maintaining acceptable doses to organs-at-risk. Real-time MR-cine imaging demonstrated sufficient quality for the automatic beam gating algorithm to provide intrafraction motion management of the spinal canal utilizing a 3.0 mm gating boundary and 1–2% region of excursion allowance, in the sagittal plane. A decrease in coverage, below the 95% threshold was noted in post-treatment volumetric imaging due to lateral movement not observed during real-time gating.Conclusion: Achieved plan quality and deliverability was within accepted standards. MR-guidance with an on-line ART workflow offered increased accuracy in the localization of the spinal cord at the time of treatment to enhance both tissue sparing and target volume coverage. Increased spatial resolution of cine-images, and tracking in three-dimensions would be beneficial for future spine-SBRT treatments on the MR-Linac.

Dosimetric analysis of MR-LINAC treatment plans for salvage spine SBRT re-irradiation.

PurposeWe investigated the feasibility of thoracic spine stereotactic body radiotherapy (SBRT) using the Elekta Unity magnetic resonance‐guided linear accelerator (MRL) in patients who received prior radiotherapy. We hypothesized that Monaco treatment plans can improve the gross tumor volume minimum dose (GTVmin) with spinal cord preservation and maintain consistent plan quality during daily adaptation.MethodsPinnacle clinical plans for 10 patients who underwent thoracic spine SBRT (after prior radiotherapy) were regenerated in the Monaco treatment planning system for the Elekta Unity MRL using 9 and 13 intensity‐modulated radiotherapy (IMRT) beams. Monaco adapt‐to‐position (ATP) and adapt‐to‐shape (ATS) workflow plans were generated using magnetic resonance imaging with a simulated daily positional setup deviation, and these adaptive plans were compared with Monaco reference plans. Plan quality measures included target coverage, Paddick conformity index, gradient index, homogeneity index, spinal cord D0.01cc, esophagus D0.01cc, lung V10, and skin D0.01cc.ResultsGTVmin values from the Monaco 9‐beam and 13‐beam plans were significantly higher than those from Pinnacle plans (p < 0.01) with similar spinal cord dose. Spinal cord D0.01cc, esophagus D0.01cc, and lung V10 did not statistically differ among the three plans. The electron‐return effect did not induce remarkable dose effects around the lungs or skin. While in the ATP workflow, a large increase in GTVmin was observed at the cost of a 10%–50% increase in spinal cord D0.01cc, in the ATS workflow, the spinal cord dose increase was maintained within 3% of the reference plan.ConclusionThese findings show that MRL plans for thoracic spine SBRT are safe and feasible, allowing tumor dose escalation with spinal cord preservation and consistent daily plan adaptation using the ATS workflow. Careful plan review of hot spots and lung dose is necessary for safe MRL‐based treatment.

Single and Multifraction Spine Stereotactic Body Radiation Therapy and the Risk of Radiation Induced Myelopathy

PurposeThis study reports on the risk of radiation-induced myelitis (RM) of the spinal cord from a large single-institutional experience with 1 to 5 fraction stereotactic body radiation therapy (SBRT) to the spine. Methods and MaterialsA retrospective review of patients who received spine SBRT to a radiation naïve level at or above the conus medullaris between 2007 and 2019 was performed. Local failure determination was based on SPIne response assessment in Neuro-Oncology criteria. RM was defined as neurologic symptoms consistent with the segment of cord irradiated in the absence of neoplastic disease recurrence and graded by Common Toxicity Criteria for Adverse Events, version 4.0. Rates of adverse events were estimated and dose-volume statistics from delivered treatment plans were extracted for the planning target volumes and spinal cord. ResultsA total of 353 lesions in 277 patients were identified that met the specified criteria, for which 270, 70, and 13 lesions received 1-, 3-, and 5-fraction treatments, respectively, with a median follow-up of 46 months (95% confidence interval [CI], 41-52 months) for all surviving patients. The median overall survival was 33.0 months (95% CI, 29-43). The median D0.03cc to the spinal cord was 11.7 Gy (interquartile range [IQR], 10.5-12.4), 16.7 Gy (IQR, 12.8-20.6), and 26.0 Gy (IQR, 24.1-28.1), for 1-, 3-, 5-fractions. Using an a/b = 2Gy for the spinal cord, the median single-fraction equivalent-dose (SFED2) was 11.7 Gy (IQR, 10.2-12.5 Gy) and the normalized biological equivalent dose (nBED2/2) was 19.9 Gy (IQR, 15.4-22.8 Gy). One patient experienced grade 2 RM after a single-fraction treatment. The cumulative probability of RM was 0.3% (95% CI, 0%-2%). ConclusionsSpine SBRT is safe while limiting the spinal cord (as defined on treatment planning magnetic resonance imaging or computed tomography myelogram) D0.03cc to less than 14 Gy, 21.9 Gy, and 30 Gy, for 1, 3, and 5-fractions, consistent with standard guidelines.

Radiation myelopathy following stereotactic body radiation therapy for spine metastases.

Stereotactic body radiation therapy (SBRT) is now considered a standard of care treatment option in the management of spine metastases. One of the most feared complications of spine SBRT is radiation myelopathy (RM). We provided a narrative review of RM following spine SBRT based on review of the published literature, including data on spinal cord dose constraints associated with the risk of RM, strategies to mitigate the risk, and management options for RM. There are limited published data of cases of RM following spine SBRT with detailed spinal cord dosimetry. The HyTEC report provided recommendations for the point maximal dose (Dmax) for the spinal cord that is associated with a < 5% risk of RM for 1-5 fractions spine SBRT. In the setting of spine SBRT reirradiation after previous conventional external beam radiation therapy (cEBRT), factors associated with RM are: SBRT spinal cord Dmax, cumulative spinal cord Dmax, and the time interval between previous RT and SBRT reirradiation. There are various strategies to mitigate the risk of RM, including accurate delineation of the spinal cord (or thecal sac), strict adherence to the recommended spinal cord dose constraints, and robust treatment immobilisation set-up and delivery. Limited effective treatment options are available for patients who develop RM, and these include corticosteroids, hyperbaric oxygen, and bevacizumab; however, none have been supported by high quality evidence. RM is a rare but devastating complication following SBRT for spine metastases. There are strategies to minimise the risk of RM to ensure safe delivery of spine SBRT.

Spine Stereotactic Body Radiotherapy to Three or More Contiguous Vertebral Levels.

BackgroundWith survival improving in many metastatic malignancies, spine metastases have increasingly become a source of significant morbidity; achieving durable local control (LC) is critical. Stereotactic body radiotherapy (SBRT) may offer improved LC and/or symptom palliation. However, due to setup concerns, SBRT is infrequently offered to patients with ≥3 contiguous involved levels. Because data are limited, we sought to evaluate the feasibility, toxicity, and cancer control outcomes of spine SBRT delivered to ≥3 contiguous levels.MethodsWe retrospectively identified all SBRT courses delivered between 2013 and 2019 at a tertiary care institution for postoperative or intact spine metastases. Radiotherapy was delivered to 14–35 Gy in 1–5 fractions. Patients were stratified by whether they received SBRT to 1–2 or ≥3 contiguous levels. The primary endpoint was 1-year LC and was compared between groups. Factors associated with increased likelihood of local failure (LF) were explored. Acute and chronic toxicity was assessed. In-depth dosimetric data were collected.ResultsOverall, 165 patients with 194 SBRT courses were identified [54% were men, median age was 61 years, 93% had Karnofsky Performance Status (KPS) ≥70, and median follow-up was 15 months]. One hundred thirteen patients (68%) received treatment to 1–2 and 52 to 3–7 (32%) levels. The 1-year LC was 88% (89% for 1–2 levels vs. 84% for ≥3 levels, p = 0.747). On multivariate analysis, uncontrolled systemic disease was associated with inferior LC for patients with ≥3 treated levels. No other demographic, disease, treatment, or dosimetric variables achieved significance. Rates of new/progressive fracture were equivalent (8% vs. 9.5%, p = 0.839). There were no radiation-induced myelopathy or grade 3+ acute or late toxicities in either group. Coverage of ≥95% of the planning target volume with ≥95% prescription dose was similar between groups (96% 1–2 levels vs. 89% ≥3 levels, p = 0.078).ConclusionsFor patients with ≥3 contiguous involved levels, spine SBRT is feasible and may offer excellent LC without significant toxicity. Prospective evaluation is warranted.

Mature Local Control and Reirradiation Rates Comparing Spine Stereotactic Body Radiation Therapy With Conventional Palliative External Beam Radiation Therapy

Stereotactic body radiation therapy (SBRT) improves complete pain response for painful spinal metastases compared with conventional external beam radiation therapy (cEBRT). We report mature local control and reirradiation rates in a large cohort of patients treated with SBRT versus cEBRT enrolled previously in the Canadian Clinical Trials Group Symptom Control 24 phase 2/3 trial. One hundred thirty-seven of 229 (60%) patients randomized to 24 Gy in 2 SBRT fractions or 20 Gy in 5 cEBRT fractions were retrospectively reviewed. By including all treated spinal segments, we report on 66 patients (119 spine segments) treated with SBRT and 71 patients (169 segments) treated with cEBRT. The primary outcomes were magnetic resonance-based local control and reirradiation rates for each treated spine segment. The median follow-up was 11.3 months (interquartile range, 5.3-27.7 months), and median overall survival in the SBRT and cEBRT cohorts were 21.6 (95% confidence interval [CI], 11.3, upper bound not reached) and 18.9 (95% CI, 12.2-29.1) months (P = .428), respectively. The cohorts were balanced with respect to radioresistant histology and presence of mass (paraspinal and/or epidural disease extension). Risk of local failure after SBRT versus cEBRT at 6, 12, and 24 months were 2.8% (95% CI, 0.8%-7.4%) versus 11.2% (95% CI, 6.9%-16.6%), 6.1% (95% CI, 2.5%-12.1%) versus 28.4% (95% CI, 21.3%-35.9%), and 14.8% (95% CI, 8.2-23.1%) versus 35.6% (95% CI, 27.8%-43.6%), respectively (P < .001). cEBRT (hazard ratio [HR], 3.48; 95% CI, 1.94-6.25; P < .001) and presence of mass (HR, 2.07; 95% CI, 1.29-3.31; P = .002) independently predicted local failure on multivariable analysis. The 1-year reirradiation rates and median times to reirradiation after SBRT versus cEBRT were 2.2% (95% CI, 0.4-7.0%) versus 15.8% (95% CI, 10.4%-22.3%) (P = .002) and 22.9 months versus 9.5 months, respectively. cEBRT (HR, 2.60; 95% CI, 1.27-5.30; P = .009) and radioresistant histology (HR, 2.00; 95% CI, 1.12-3.60; P = .020) independently predicted for reirradiation. Eight of 12 iatrogenic vertebral compression fractures were after SBRT and 4 of 12 after cEBRT; grade 3 adverse fracture effects were isolated to the SBRT cohort (5 of 12). Risk of local failure and reirradiation is lower with SBRT compared with cEBRT for spinal metastases. Although the iatrogenic vertebral compression fracture rates were within expectations, grade 3 vertebral compression fractures were isolated to the SBRT cohort.

Deviation from consensus contouring guidelines predicts inferior local control after spine stereotactic body radiotherapy

Background and purposeTo analyze the impact of target delineation on local control (LC) after stereotactic body radiotherapy (SBRT) for spine metastasis. Materials and methodsPatients with de novo metastasis of the spine treated with SBRT, excluding those with prostate or hematologic malignancies, were retrospectively reviewed. Deviations from consensus contouring guidelines included incomplete coverage of involved vertebral compartments, omission of adjacent compartments, or unnecessary circumferential coverage. Univariable and multivariable Cox proportional hazard analyses were performed using death as a competing risk. Results283 patients with 360 discrete lesions were included with a median follow up of 14.6 months (range 1.2–131.3). The prescription dose was 24–27 Gy in 2–3 fractions for the majority of lesions. Median survival after SBRT was 18.3 months (95 % confidence interval [CI]: 14.8–22.8). The 1 and 2-year local control (LC) rates were 81.1 % (95 % CI: 75.5–85.6 %) and 70.6 % (95 % CI: 63.2–76.8 %), respectively. In total, 60 deviations (16.7 %) from consensus contouring guidelines were identified. Deviation from guidelines was associated with inferior LC (1-year LC 63.0 % vs 85.5 %, p < 0.001). Gastrointestinal primary, epidural extension, and paraspinal extension were all associated with inferior LC on univariable analyses. After adjusting for confounding factors, deviation from guidelines was the strongest predictor of inferior LC (HR 3.52, 95 % CI: 2.11–5.86, p < 0.001). Among guideline-compliant treatments, progressions were mainly in field (61 %) and/or epidural (49 %), while marginal (42 %) and/or epidural progressions (58 %) were most common for those with deviations. ConclusionsAdherence to consensus contouring guidelines for spine SBRT is associated with superior LC and fewer marginal misses.

Stereotactic body radiotherapy for spinal metastases: a review.

To evaluate the efficacy and safety of stereotactic body radiotherapy (SBRT) in treating spinal metastases. Two reviewers performed independent literature searches of the PubMed database, searching literatures of the efficacy and safety of SBRT in metastatic spinal diseases. A total of 67 studies were included in the review. Regarding SBRT for de novo spinal metastases, the 1- and 2-year local control (LC) rates were 51-100% and 56-96%, respectively. The local failure rate was 10.5-47.5%, with most studies reporting a local failure rate of < 30%. The 1- and 2-year overall survival (OS) rates were 25.7-80% and 25-60.7%, respectively. The pain relief rate was 41.6-100%. In the postoperative scenario, the LC rate was 70-100%, and the local failure rate was 11.7-33%. Regarding the reirradiated setting, the 1-year LC rate was 71-83%, the local failure rate was 6.0-25.5%, and the 1-year OS rate was 28-68%. The pain relief rate was approximately 35.7-77%. Between studies on single- and multi-fraction SBRT, the 1- and 2-year LC rates with single-fraction SBRT were 71-95% and 70-96%, respectively; the 1- and 2-year OS rates with single-fraction SBRT were 43.5-46% and 43.5-49%, respectively. For the management of spinal metastases, it appears that regardless of the clinical scenario in which SBRT is applied, a high rate of LC is achieved, particularly with single-fraction SBRT, regardless of histology. Additionally, spinal SBRT can establish durable pain palliation with acceptable toxicities.

Feasibility of postoperative spine stereotactic body radiation therapy in proximity of carbon and titanium hybrid implants using a robotic radiotherapy device

Background and purposeTo assess the feasibility of postoperative stereotactic body radiation therapy (SBRT) for patients with hybrid implants consisting of carbon fiber reinforced polyetheretherketone and titanium (CFP-T) using CyberKnife.Materials and methodsAll essential steps within a radiation therapy (RT) workflow were evaluated. First, the contouring process of target volumes and organs at risk (OAR) was done for patients with CFP-T implants. Second, after RT-planning, the accuracy of the calculated dose distributions was tested in a slab phantom and an anthropomorphic phantom using film dosimetry. As a third step, the accuracy of the mandatory image guided radiation therapy (IGRT) including automatic matching was assessed using the anthropomorphic phantom. For this goal, a standard quality assurance (QA) test was modified to carry out its IGRT part in presence of CFP-T implants.ResultsUsing CFP-T implants, target volumes could precisely delineated. There was no need for compromising the contours to overcome artifact obstacles. Differences between measured and calculated dose values were below 11% for the slab phantom, and at least 95% of the voxels were within 5% dose difference. The comparisons for the anthropomorphic phantom showed a gamma-passing rate (5%, 1 mm) of at least 97%. Additionally the test results with and without CFP-T implants were comparable. No issues concerning the IGRT were detected. The modified machine QA test resulted in a targeting error of 0.71 mm, which corresponds to the results of the unmodified standard tests.ConclusionDose calculation and delivery of postoperative spine SBRT is feasible in proximity of CFP-T implants using a CyberKnife system.